Field of the Invention
The present invention relates to a power connector for receiving an electric plug, and more particularly to a power connector provided with an improved safety shutter, allowing the invention to meet the strict international safety standards for household plugs, adapters and socket-outlets.
Description of Related Art
Many European countries, including Portugal, Finland, Denmark, Norway and Sweden, require installment of safety shutters in socket outlets to prevent children from poking objects into them. To meet the requirement that the socket shutters can be opened up only when the live and neutral poles of a plug are inserted at the same time, some single-piece shutter designs have been proposed in the art, such as those disclosed in Great Britain Patent Publication Nos. 793000 and 2199996. However, such designs were frequently found hard to operate, as considerable force was needed to drive the relatively large shutter plate to its open position. It has also been found that the safety shutters of some conventional sockets will fail to work and the receiving surfaces of the safety shutters can wear out quickly, when receiving an electric plug with relatively sharp edges, such as a typical US polarized plug 9 having an edge inclined at 50° relative to its flat tip as shown in FIG. 6. The shortcomings are likely due to the small contact area between the plug tips and the safety shutters, as well as the relatively weak component force produced in the direction perpendicular to the insertion direction.
Additional problems may arise due to the limited space which the shutter plate must share with other elements in the socket cavity. For example, referring to the traditional universal socket arrangement illustrated in FIG. 14, an upright grounding system 50″″ is disposed at the center of the socket cavity and, thus, the shutter plate 30″″ is spatially hindered from moving towards the grounding system 50″″. To address this issue, the shutter plate 30″″ was arranged to open up the outlets by moving away from the grounding system 50″″. As a consequence, the traditional device is unsatisfactorily large in size and the portability thereof is undesirably compromised. Moreover, when a socket of this type receives a Schuko CEE 7/4 plug having flat grounding contacts, the safety shutters 30″″, biased by the spiral springs 33″″, apply a force to the live and neutral poles of the Schuko plug and, therefore, tend to push the plug away from the grounding metal of the socket to create a gap between the plug and the socket, causing a poor grounding connection. An unofficial test conducted by the inventors showed that the conventional safety shutters could disadvantageously lead to unreliable grounding connection at a defect rate as high as 40%.
The co-pending U.S. application Ser. No. 14/683,248, assigned to the present applicant, discloses a power connector provided with a three-piece safety shutter architecture. In this architecture, a pair of safety shutters are interlocked with each other by slidably engaging the guide members of the safety shutters with the tabs extending from a traversely movable locking bar, where one of the guide members is in the form of a guide groove and the other is in the form of a side wall of the safety shutters. While the three-piece safety shutter architecture was proved to overcome the disadvantages above to a great extent, there remains a need for an improved power connector device that can fulfill the national safety requirements, especially when receiving a Schuko plug that is normally designed to be insertable in either way.